Specific heat indicator



Ytion during which conditions might change.

United States Patent' 0 SPECIFIC HEAT INDICATOR Frederick L. Horn, Sa'yville, and John E. Binns,

Roslyn, N.Y., assignors to the United States of America as represented by the United States Atomic Energy Commission Filed Sept. 9, 19.58, Sel'. No. 760,048

5 Claims. (Cl. 'I3-193) The present invention relates to apparatus for determining specic heat and, more particularly, to electrical apparatus for continuously measuring and computing the Y requires particular data on the rate of ow of the solution, its specific gravity, and its ability to transfer heat, from which the calculations are made to determine this characteristic. Heretofore, measurements and readings have been made at particular intervals, followed by the necessary calculations, so it was only possible to make spot checks on the operation of the process. One inherent disadvantage of this Way of determining the specific heat of continuously etiowing solutions lies in the time which must elapse between measurement and determina- Another disadvantage is that unless measurements and calcula- ,tions are being made continuously, no complete picture of the solution is possible, with the attendant lack of precise control over the chemical process going on.

These and other disadvantages of the aforementioned technique of computing the speciiic heat of a continuously flowing solution are overcome by the instant invention which, briey described, comprises apparatus for measuring the various parameters necessary to compute speciiic heat and automatically combining them to produce the desired information, in continuous form. For this purpose, there is provided in one preferred embodiment a liquid cooled heat exchanger in heat exchange relationship with the iiowing solution. The apparatus takes data from the heat exchanger and the owing solution and, by the use of a novel arrangement including logarithmic potentiometers, continuously solves the equation where Cp is thev specic heat of the solution being deternnned,V

Vw is the volumetric rate of tlow of the coolant (Water), dtw is lthe temperature rise of the coolant,

sgs is the'specitic gravity of the solution,

Vs is the'volumetric rate of ilow of the solution, and dts isthe ten;\peratl1 reV drop of the"solution.

The abovedata furnished by suitable sensing .instruments which supply electrical signals for solving the equation, as

described in detail further below.

It is lthus' arrst object of this invention to' provide ticular parameters undergoing measurement for .carrying out the mathematical operations involved.

It is still another object of this invention to provide a null-seeking analog computer utilizing a plurality of logarithmic potentiometers and additional means for eliminatng ambiguities arising out of values less than unity.

These and other objects will become more readily apparent from the following description of the drawing which is a schematic' illustration of a preferred form of this invention.

Referring to the drawing, there is shown a conduit 10 for conveying a liquid solution -12 which is subject to the measurement of specific heat by the inventive apparatus generally indicated by 14. Mounted in a manner understood in the art yis Va liquid cooled heat exchanger 16 of convenient and conventional design having inlet and outlet pipes 18 and 20, respectively, for permitting ingress and egress of the coolant 22, which in this arrangement is water. -It is understood that heat exchanger 16 may be a heater and that heat can be transferred to solution 10 instead ofextracted.

For the purposes of measuring and indicating the vari ous parameters involved, there are provided a plurality of instruments described below. A conventional or commercially available volumetric fiowmeter 23 such as the Rotameter produced by Schutte & Koerting Co. may be located in line 18 to measure and indicate the volumetric flow of coolant 22. By a common mechanical connection 31 schematically illustrated, instrument 23 is connected to move wiper 32 of a logarithmic potentiometer 34 to position the former in accordance with the magnitude of ow measured by owmeter 23. As is understood in the art, potentiometer wiper 32 will select a signal which is proportional to the logarithm of this magnitude. A conventional temperature measuring instrument 24, such as a Thermocouple Temperature Recorder manufactured by the Brown Instrument Co., is connected as c illustrated schematically by electrical lead lines 24a and 24b to measure the temperature changes occurring in coolant 22 as a result of its passage through heat exchanger 16. Ina manner similar to that described in connection with flowmeter 23, temperature'measuring'in-Y strument 24 by the mechanical linkage 35 positions wiper 36 on a logarithmic potentiometer 38 to select a logarithmic signal in proportion to the magnitude of the temperature change which is produced in coolant 22. A

' third instrument 26, which may be the Liquid Level Transmitter manufactured by the Moore Products Co., is connected by sampling tube 26a or `other convenient means to conduit-10 and measures the specific gravity of solution 12 and positions, through mechanical linkage 39, wiper 40 on logarithmic potentiometer 42 to produce a proportional logarithmic signal as a result thereof. A fourth instrument, flowmeter 28, also of conventional design, is located in solution conduit 10 for the purpose of measuring and indicating the volumetric ow of solution 12V therethrough and, in a manner similar to the Vprevious instruments described, will position Via mechanical connection 43 the Wiper. 44 of logarithmic potenti-l onreter 46. A fth and final measuring instrumen t,'a tern- Y, `perature measuring Vdevice 39 of common variety, is provided to measure the temperature change of solution'12 as a result of its passage through heat exchanger 16. A pair `ot electricallead connections I30av and 30bis provided of the temperature change measured by instrument A30.

Recording instruments 23,-' 24, 26528", and 30 as already indicated are allwell known `in the art and may be se- 'lected in accordance with` thefrange of;v operating co'ndi.-` I

Y transformers 52, "5.4, 56, 58 and 60.' It Will be seen from the drawing that the primary coils of these transformers along with additional transformers 62 and 64 to be described further below are connected in parallel across a 11o-volt, 60-cycle source for energization. The secondary coils of these transformers are connected across their associated potentiometer windings to produce the full voltage thereacross. It will be noted from the use of signs to indicate phase at the ends of the potentiometers that the Various potentiometer windings are electrically connected together in a particular fashion to be -now described. VIn order to carry outV the multiplication and division' operations of the formula given above for specic heat, wiper 32 is connectedV electrically to the positive end of potentiometer 38. .The positive end of'potentiometer 34 is connected to wiper 48 of potentiometer 50; wiper 44 is connected to the negative end of potentiometer 50; and wiper 40 Vis connected to the negative end of potentiometer 46. By this arrangement, it is seen thatV the alternating voltage signals on potentiometers 34 and 38 are additive (in phase) with'respect to each other, while in a similar fashion the signals on potentiometers 42, 46 and 50 are also additive with respect to each other.

Instrument Co. designed to position wiper 76 to select a signal equal and opposite in phase to the input signal found across a pair of contacts T-2 connected between wiper 76 and line 86. The position of wiper 76 is thereby directly indicative of the value of this input Signal, or, in other words, KCp. Apparatus- 80 comprises a circuit generally indicated by 82 which utilizes an amplifier and servo motor (not shown) to move wiper76 through'a linkage 84 in accordance with the signal between wiper 76 and lead 86 to select a voltage in opposition to the inputsignal and cancel the latter. The input signal to instrument 80 is understood to be the resultant of all the operations already described, or log KCp.Y The arrangement 80 insures stabilizationsof the voltage on contacts T-Z, or, that no current llow will be produced to afect the voltage on contacts T-2, thereby making the apparatus 14 a null-seeking or self-balancing type of high accuracy.

In the operation of the apparatus described above, the particular setting of wiper 74 (selection of K) is obtained as follows: Each of wipers 32, 36, 40, 44 and 48 Yis calibrated in its respective potentiometer to reflect accurately its respective instrument. Values for the settings fof the group of potentiometers 34, 3S, "42 y46 and 48 are arbi- However, the sum of the signals selected by wipers 32 A lpair of contactsYT-l are connected respectively to wiper 36- and to the negative end of potentiometer 42. Across contacts T1`, an alternating current voltage will thus appear representative of the logarithmic value of specic'heat However, because it is not readily possible to determine the phase of the signal or its significance if it is determined, the resulting signal across contacts T-l will be Vambiguous since it will not be obvious Whether 'the speciiicheat (Cp) is greater Vor less than unity depending upon whether the logarithmic value thereof'V is positive or negative as indicated by the phase of the signal. To eliminate this ambiguity'and to obtain additional 'benefits hereinafter described, it will be noted from the drawing that between potetiometers 38 and 42 (across 'i contacts T-1,) there is provided additional circuitryincluding a pair of potentiometers 70 and72 having wipers 74 and 76, respectively. Potentiometers 70'and 72 areV energized in a fashion similar to the'l other potentiometers `by their transformers 62 and `64g, respectively; It will be` seen that potentiometer 70 is connected in the arrange- Y ment so as to introduce -a signal which may bedescribed for Ythe present as theV logarithmic valueof a constant K Vselected by the manual positioning of wiper 74 by a knobV 7,5. signal is additive (in phase) with `respect to those on potentiometers 34`and 38.v VThe Voltage added by potentiometer 7),fasj noted, represents theVV logarithm of a factorK bywhichrCp is multiplied, and the voltage across the terminals T-2 would thus be indicated by the p expression in a Vmanner which will be described further below. In

1 V-this Way, thephase of the signal across contacts T-1 willY never change, v'and the specific-heat as'computed will be multiplied by'some constant K, identified above.Y Y

VPotentiometer 72;.is"'connected to introduce a-Vsignal K,

oppositerinphase-rtowthatof K.j For this purpose -it is iWiper wouldfbe positioned 'manually to, select log Y trarily set and the specific heat is calculated. Wiper '/"4 is adjusted so that recorder 8) presents the calculated reading, and then K as ydetermined bythe position of wiper 74 may be calculated. Wiper 76 may beV provided with a log conversion dial (not shown) for reading directly in specific heat. Y Y Y It is thus seen that there has been provided apparatus for producing the continuous and accurate measurement of the specific heat of a owingsolutiommaking the apparatus particularly adaptable for use in chemical processes. As a result, changes in the process required by variations in specific heat can be brought about quickly vand efciently without disturbing or interrupting the flow of the solution undergoing chemical treatment. Furthermore, it is seen that with the use of this invention no handling of the solution undergoing measurement is Yrequired as in the other ways of measuring specific heat, previously mentioned. This is an important vfeature of the invention when the fluid being processed is highly corrosive or otherwise dithcult to handle, asfor example the materials described in U.S. Patent No. 2,830,874, in-

cluding uranium hexauoride.

' Obviously many modifications' and Vvariations of the present invention are possible in the light of the above teachings. For example, it Ahas already been noted that the apparatus described above is designed for useV where the coolant is water having a specific gravity 'of Yunity to which solution 12 is compared. However, the apparatus can be adapted for use with other coolantsfrby incorporating twoV additional potentiometer 'voltage suppliers. One of these can be manually adjusted to provide a voltage equivalent of thelogarithm ofthe speciiic heat of the coolant other than water and the second actuated by a device similar to instrument 26 to indicate the specific gravity of the coolant and provide a Voltage representing jthe logarithm of `said specic gravity. So modified .thel 'circuit would then solve the equation whereinthev Ysubscriptc pertains 4to the coolant and the Y i subscript sipertainsto the solution.

It is thereforeto be understood Ythat within the lscope of the' appended claims the invention may be'evpractice-d otherwise than as Yspecifically, described.

' l.-Apparatus for providing an indication of Athespeeiflc heat of :a 'flowing Vsolution comprising, in; combination, means for placing a ilowing liquidfin heat verich-urgerelationship with saidlisolution, lirstmeans lfor providing an alternatingfjvoltage,asa function .of theyolurnetric `irate of flow foisaid liquid, .second for "providing y anvv alternating Voltage as a function ,of the temperature change of said liquid due to said heat exchange relationship, third means for providing an alternating voltage as a function of the specific gravity of said solution, fourth means for providing an alternating voltage as a function of the volumetric rate of ow of said solution, fifth means for providing an alternating voltage as a function of the temperature change of said solution due to said heat exchange relationship, and means for producing a tinal voltage in proportion to the product of said voltages produced by said iirst and second means and in inverse proportion to the product of said voltages produced by said third, fourth and fth means representative of said specic heat.

2. Apparatus for determining the specic heat (Cp) of a ilowing solution comprising, in combination, means for placing arowing liquid in heat exchange relationship with said solution, rst means for providing an alternating voltage as a function of the logarithm of the volumetric rate of ow (VW) of said liquid, second means for providing an alternating voltage as a function of the logarithm of the temperature change (dlw) of said liquid due to said heat exchange relationship, third means for providing an alternating voltage as a function of the logarithm of the specic gravity (sgg) of said solution, fourth means for providing an alternating voltage as a function of the logarithm of the volumetric rate of ow (Vs) of said solution, fifth means for providing an alter nating voltage as a function of the logarithm of the temperature change of said solution (dts) due to said heat exchange relationship, and means for combining said voltages in accordance with the relation and thereby provide a voltage indicating said specific heat.

3. Apparatus for providing an indication of the specic heat of a owing solution comprising in combination, means for placing a flowing liquid in heat exchange relationship with said solution, first means for providing an alternating voltage proportional to the logarithm of the volumetric rate of ow of said liquid, second means for providing an `alternating voltage proportional to the logarithm of the temperature change of said liquid due to said heat exchange relationshhip, third means for providing an alternating voltage proportional to the logarithm of the specic gravity of said solution, fourth means for providing an alternating voltage proportional to the logarithm of the volumetric rate of flow of said solution, a iifth means for providing an alternating voltage proportional to the logarithm of the temperature change of said solution due to said heat exchange relationship, means for producing -a nal voltage in proportion to the product of said voltages produced by said first and second means and in inverse proportion to the product of said voltages produced by said third, fourth and fth means representative of said specific heat, and means for adding a predetermined constant voltage of suiiicient magnitude to be combined with the other said voltages for insuring a particular phase of said final voltage.

4. IApparatus for providing an indication of the specic heat of a owing solution comprising in combination,

means for placing a owing liquid in heat exchange relationship with said solution, rst means for providing an alternating voltage proportional to the logarithm of the volumetric rate of iiow of said liquid, second means for 0 providing an alternating voltage proportional to the logarithm of the temperature change of said liquid due to said heat exchange relationship, third means for providing an alternating voltage proportional to the logarithm of the specific gravity of said solution, fourth means for 10 providing an alternating voltage proportional to the logarithm of the volumetric rate of flow of said solution, a lifth means for providing an alternating voltage proportional to the logarithm of the temperature change of said solution due to said heat exchange relationship, means for summing said voltages produced by said iirst and second means and subtracting said voltages produced by said third, fourth and fifth means and producing a nal voltage indicative of said specific heat, and nullseeking means for adding a voltage opposite in phase and equal in magnitude to said nal voltage and thereby reduce current ow and stabilize the magnitude of said final voltage.

5. Apparatus for providing an indication of the speciiic heat of a iiowing solution comprising in combination, 20 means for placing a flowing liquid in heat exchange relationship with said solution, rst means for providing an alternating voltage proportional to the logarithm of the volumetric rate of ow of said liquid, second means for providing an alternating voltage proportional to the logarithm of the temperature change of said liquid due to said heat exchange relationship, third means for providing an alternating voltage proportional to the logarithm of the specic gravity of said solution, fourth means for providing an alternating voltage proportional to the logarithm of the volumetric rate of ow of said solution, a fifth means for providing an alternating voltage proportional to the logarithm of the temperature change of said solution due to said heat exchange relationship, means for summing said voltages produced by said rst and second means and subtracting said voltages produced by said third, fourth and fifth means and producing a tinal voltage indicative of said specific heat, means for adding a predetermined constant voltage of suicient magnitude to be combined with the other said voltages for insuring -a particular phase of said nal voltage, and null-seeking means for adding a voltage opposite in phase and equal in magnitude to said final voltage and thereby reduce current flow and stabilize the magnitude of said final voltage.

References Cited in the le of this patent UNITED STATES PATENTS 1,573,850 Neiman Feb. 23, 1926 FOREIGN PATENTS 235,651 Switzerland May 1, 1945 6o OTHER REFERENCES 31 Ways to Multiply, by Sidney A. Davis, Control Engineering, vol. 1, No. 3, November 1954. 

